Author: Payne D Flaherty S P Barry M F Matthews C D
Publisher: Oxford University Press
ISSN: 1460-2350
Source: Human Reproduction, Vol.12, Iss.3, 1997-03, pp. : 532-541
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Abstract
In this study, we have used time-lapse video cinematography to study fertilization in 50 human oocytes that had undergone intracytoplasmic sperm injection (ICSI). Time-lapse recording commenced shortly after ICSI and proceeded for 17-20 h. Oocytes were cultured in an environmental chamber which was maintained under standard culture conditions. Overall, 38 oocytes (76%) were fertilized normally, and the fertilization rate and embryo quality were not significantly different from 487 sibling oocytes cultured in a conventional incubator. Normal fertilization followed a defined course of events, although the timing of these events varied markedly between oocytes. In 35 of the 38 fertilized oocytes (92%), there were circular waves of granulation within the ooplasm which had a periodicity of 20-53 min. The sperm head decondensed during this granulation phase. The second polar body was then extruded, and this was followed by the central formation of the male pronucleus. The female pronucleus formed in the cytoplasm adjacent to the second polar body at the same time as, or slightly after, the male pronucleus, and was subsequently drawn towards the male pronucleus until the two abutted. Both pronuclei then increased in size, the nucleoli moved around within the pronuclei and some nucleoli coalesced. During pronuclear growth, the organelles contracted from the cortex towards the centre of the oocyte, leaving a clear cortical zone. The oocyte decreased in diameter from 112 to 106 microm (P < 0.0001)="" during="" the="" course="" of="" the="" observation="" period.="" the="" female="" pronucleus="" was="" significantly="" smaller="" in="" diameter="" than="" the="" male="" pronucleus="" (24.1="" and="" 22.4="" microm="" respectively,="" p="0.008)" and="" contained="" fewer="" nucleoli="" (4.2="" and="" 7.0="" respectively,="" p="">< 0.0001).="" after="" time-lapse="" recording,="" oocytes="" were="" cultured="" for="" 48="" h="" prior="" to="" embryo="" transfer="" or="" cryopreservation.="" embryo="" quality="" was="" related="" to="" fertilization="" events="" and="" periodicity="" of="" the="" cytoplasmic="" wave,="" and="" it="" was="" found="" that="" good="" quality="" embryos="" arose="" from="" oocytes="" that="" had="" more="" uniform="" timing="" from="" injection="" to="" pronuclear="" abuttal="" and="" tended="" to="" have="" a="" longer="" cytoplasmic="" wave.="" in="" conclusion,="" we="" have="" shown="" that="" time-lapse="" video="" cinematography="" is="" an="" excellent="" tool="" for="" studying="" fertilization="" and="" early="" embryo="" development,="" and="" have="" demonstrated="" that="" human="" fertilization="" comprises="" numerous="" complex="" dynamic="" events.="">
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